The call came in as unassigned.  The person at the other end stated his name was Alex (Indian accent) and said he was with Microsoft Windows.  He stated that a powerful/harmful virus was detected in my computer and he wanted to talk me through some steps to get it fixed.  

I didn't let him waste too much of my time, just asked why he couldn't just email me the instructions to fix it...he said I couldn't fix it because I'm not a technician.  I told him I was in the middle of something and would call him right back and, surprise, he immediately hung up.  

I'm guessing he was attempting to get information that would allow him to hack into my computer.